Coral diseases contribute to the decline of reef communities, but factors that lead to disease ar... more Coral diseases contribute to the decline of reef communities, but factors that lead to disease are difficult to detect. In the present study, we develop a multi-species model of colony-scale risk for the class of coral diseases referred to as White Syndromes, investigating the role of current or past conditions, including both environmental stressors and biological drivers at the colony and community scales. Investigating 7 years of coral survey data at five sites in Guam we identify multiple environmental and ecological associations with White Syndrome, including a negative relationship between short-term heat stress and White Syndrome occurrence, and strong evidence of increasing size-dependent White Syndrome risk across coral species. Our findings result in a generalized model used to predict colony-scale White Syndrome risk for multiple species, highlighting the value of long-term monitoring efforts to detect drivers of coral disease.
Herbivorous reef fishes are an important component of coral reef ecosystems and a focal point in ... more Herbivorous reef fishes are an important component of coral reef ecosystems and a focal point in reef management. Herbivore diets have been examined using a myriad of methods, making it difficult to compare between analyses and to examine consistency or variability in diet across large spatial scales or heterogeneous environments. Here, we present a method to quantify and validate the diet diversity of these important coral reef species. We compile a database of information on Pacific herbivorous reef fishes through a systematic review of published diet data, and for those studies in which appropriate information is reported, we calculate a single Simpson's Diversity Index value to represent the diet diversity of each. We then validate this approach by examining the diet diversity of five species using DNA metabarcoding to sequence the algae present in their stomach contents. The two approaches provided comparable estimates of diet diversity, and we find evidence for considerabl...
Surgeonfishes (Acanthuridae) are an important group of herbivores that are abundant on reefs glob... more Surgeonfishes (Acanthuridae) are an important group of herbivores that are abundant on reefs globally. Acanthurids consume macroalgae that can compete with corals for space, turf algae that can proliferate on degraded reefs, and detritus that may smother adult corals or inhibit settlement. For these reasons, they are of particular interest at present to resource managers seeking to restore and conserve reefs that are facing a myriad of stressors. To contribute to our understanding of the diet breadth and potential vulnerability of these important fishes, we employed metabarcoding to identify and compare the algal diets of two common Hawaiian surgeonfishes, the convict tang or manini (Acanthurus triostegus) and the brown surgeonfish or maʻiʻiʻi (A. nigrofuscus). These species serve important biological and cultural roles in Hawaiian coral reef ecosystems, and manini, in particular, constitute an essential component of traditional Hawaiian diets. Although diet richness was not signifi...
Novel methodologies now make it possible to track the complete geographical movements of seafood ... more Novel methodologies now make it possible to track the complete geographical movements of seafood species from reproduction to human consumption. Doing so will better inform consumers and assist resource managers in matching fisheries and conservation policies with natural borders and pathways, including stock boundaries, networks of marine protected areas, and fisheries management areas. Such mapping necessitates an unprecedented synthesis of natural and social sciences, including knowledge of adult fish population abundance and movements, egg output, larval dispersal, and recruitment to juvenile and adult habitats, as well as fisheries stock assessment, capture, and distribution through human social networks. The challenge is to fully integrate oceanography, population genetics, ecology, and social sciences with fisheries biology to reveal the patterns and mechanisms of “Fish Flow” from spawning to supper. As practitioners representing all five of these disciplines, we believe that...
Remotely sensed ocean color data are useful for monitoring water quality in coastal environments.... more Remotely sensed ocean color data are useful for monitoring water quality in coastal environments. However, moderate resolution (hundreds of meters to a few kilometers) satellite data are underutilized in these environments because of frequent data gaps from cloud cover and algorithm complexities in shallow waters. Aggregating satellite data over larger space and time scales is a common method to reduce data gaps and generate a more complete time series, but potentially smooths out the small-scale, episodic changes in water quality that can have ecological influences. By comparing aggregated satellite estimates of Kd(490) with related in-water measurements, we can understand the extent to which aggregation methods are viable for filling gaps while being able to characterize ecologically relevant water quality conditions. In this study, we tested a combination of six spatial and seven temporal scales for aggregating data from the VIIRS instrument at several coral reef locations in Mau...
Coral bleaching is the single largest global threat to coral reefs worldwide. Integrating the div... more Coral bleaching is the single largest global threat to coral reefs worldwide. Integrating the diverse body of work on coral bleaching is critical to understanding and combating this global problem. Yet investigating the drivers, patterns, and processes of coral bleaching poses a major challenge. A recent review of published experiments revealed a wide range of experimental variables used across studies. Such a wide range of approaches enhances discovery, but without full transparency in the experimental and analytical methods used, can also make comparisons among studies challenging. To increase comparability but not stifle innovation, we propose a common framework for coral bleaching experiments that includes consideration of coral provenance, experimental conditions, and husbandry. For example, reporting the number of genets used, collection site conditions, the experimental temperature offset(s) from the maximum monthly mean (MMM) of the collection site, experimental light condit...
Reef corals are mixotrophic organisms relying on symbiont-derived photoautotrophy and water colum... more Reef corals are mixotrophic organisms relying on symbiont-derived photoautotrophy and water column heterotrophy. Coral endosymbionts (Family: Symbiodiniaceae), while typically considered mutualists, display a range of species-specific and environmentally mediated opportunism in their interactions with coral hosts, potentially requiring corals to rely more on heterotrophy to avoid declines in performance. To test the influence of symbiont communities on coral physiology (tissue biomass, symbiont density, photopigmentation) and nutrition (δ13C, δ15N), we sampled Montipora capitata colonies dominated by a specialist symbiont Cladocopium spp. or a putative opportunist Durusdinium glynnii (hereafter, C- or D-colonies) from Kāne‘ohe Bay, Hawai‘i, across gradients in photosynthetically active radiation (PAR) during summer and winter. We report for the first time that isotope values of reef corals are influenced by Symbiodiniaceae communities, indicative of different autotrophic capacities ...
Dissolved organic matter (DOM) composition influences microbial community metabolism and benthic ... more Dissolved organic matter (DOM) composition influences microbial community metabolism and benthic primary producers are a source of DOM in coral reefs. As reef benthic communities change, in part due to nutrient pollution, understanding impacts on reef microbial processes requires knowledge of DOM sources and composition. We conducted a multi‐week mesocosm experiment dosing four coral reef benthic constituents with three levels of nitrate and phosphate to contrast exudate composition and quantify the effects of nutrient enrichment on exudate release. Moderate nutrient enrichment enhanced bulk dissolved organic carbon exudation by all producers. Corals exuded rapidly accumulating DOM with a markedly high concentration of aromatic amino acid‐like fluorescent DOM components that clearly distinguishes them from algal exudates, which were dominated by humic‐like fluorescent components and did not accumulate significantly. Our results indicate that corals and algae release DOM of different...
Endemic disease transmission is an important ecological process that is challenging to study beca... more Endemic disease transmission is an important ecological process that is challenging to study because of low occurrence rates. Here, we investigate the ecological drivers of two coral diseases -- growth anomalies and tissue loss -- affecting five coral species in Hawaii. We first show that a statistical framework called the case-control study design, commonly used in epidemiology but rarely applied to ecology, provided high predictive accuracy (68-84%) and disease detection rates (62-86%) compared with a traditional statistical approach that yielded high accuracy (98-100%) but low disease detection rates (0-13%). Using this framework, we found that larger corals were associated with higher disease risk across all host-disease pairs. We found that human activities in watersheds adjacent to shallow, semi-protected coral reefs were associated with growth anomalies whereas reef structure, water movement, and temperature exposure were associated with tissue loss. Variation in risk factors...
The deep reef refuge hypothesis (DRRH) postulates that mesophotic coral ecosystems (MCEs) may pro... more The deep reef refuge hypothesis (DRRH) postulates that mesophotic coral ecosystems (MCEs) may provide a refuge for shallow coral reefs (SCRs). Understanding this process is an important conservation tool given increasing threats to coral reefs. To establish a better framework to analyze the DRRH, we analyzed stony coral communities in American Sāmoa across MCEs and SCRs to describe the community similarity and species overlap to test the foundational assumption of the DRRH. We suggest a different approach to determine species as depth specialists or generalists that changes the conceptual role of MCEs and emphasizes their importance in conservation planning regardless of their role as a refuge or not. This further encourages a reconsideration of a broader framework for the DRRH. We found 12 species of corals exclusively on MCEs and 183 exclusively on SCRs with another 63 species overlapping between depth zones. Of these, 19 appear to have the greatest potential to serve as reseeding...
Corals build reefs through accretion of calcium carbonate (CaCO3) skeletons, but net reef growth ... more Corals build reefs through accretion of calcium carbonate (CaCO3) skeletons, but net reef growth also depends on bioerosion by grazers and borers and on secondary calcification by crustose coralline algae and other calcifying invertebrates. However, traditional field methods for quantifying secondary accretion and bioerosion confound both processes, do not measure them on the same time-scale, or are restricted to 2D methods. In a prior study, we compared multiple environmental drivers of net erosion using pre- and post-deployment micro-computed tomography scans (μCT; calculated as the % change in volume of experimental CaCO3 blocks) and found a shift from net accretion to net erosion with increasing ocean acidity. Here, we present a novel μCT method and detail a procedure that aligns and digitally subtracts pre- and post-deployment μCT scans and measures the simultaneous response of secondary accretion and bioerosion on blocks exposed to the same environmental variation over the sam...
Coral diseases contribute to the decline of reef communities, but factors that lead to disease ar... more Coral diseases contribute to the decline of reef communities, but factors that lead to disease are difficult to detect. In the present study, we develop a multi-species model of colony-scale risk for the class of coral diseases referred to as White Syndromes, investigating the role of current or past conditions, including both environmental stressors and biological drivers at the colony and community scales. Investigating 7 years of coral survey data at five sites in Guam we identify multiple environmental and ecological associations with White Syndrome, including a negative relationship between short-term heat stress and White Syndrome occurrence, and strong evidence of increasing size-dependent White Syndrome risk across coral species. Our findings result in a generalized model used to predict colony-scale White Syndrome risk for multiple species, highlighting the value of long-term monitoring efforts to detect drivers of coral disease.
Herbivorous reef fishes are an important component of coral reef ecosystems and a focal point in ... more Herbivorous reef fishes are an important component of coral reef ecosystems and a focal point in reef management. Herbivore diets have been examined using a myriad of methods, making it difficult to compare between analyses and to examine consistency or variability in diet across large spatial scales or heterogeneous environments. Here, we present a method to quantify and validate the diet diversity of these important coral reef species. We compile a database of information on Pacific herbivorous reef fishes through a systematic review of published diet data, and for those studies in which appropriate information is reported, we calculate a single Simpson's Diversity Index value to represent the diet diversity of each. We then validate this approach by examining the diet diversity of five species using DNA metabarcoding to sequence the algae present in their stomach contents. The two approaches provided comparable estimates of diet diversity, and we find evidence for considerabl...
Surgeonfishes (Acanthuridae) are an important group of herbivores that are abundant on reefs glob... more Surgeonfishes (Acanthuridae) are an important group of herbivores that are abundant on reefs globally. Acanthurids consume macroalgae that can compete with corals for space, turf algae that can proliferate on degraded reefs, and detritus that may smother adult corals or inhibit settlement. For these reasons, they are of particular interest at present to resource managers seeking to restore and conserve reefs that are facing a myriad of stressors. To contribute to our understanding of the diet breadth and potential vulnerability of these important fishes, we employed metabarcoding to identify and compare the algal diets of two common Hawaiian surgeonfishes, the convict tang or manini (Acanthurus triostegus) and the brown surgeonfish or maʻiʻiʻi (A. nigrofuscus). These species serve important biological and cultural roles in Hawaiian coral reef ecosystems, and manini, in particular, constitute an essential component of traditional Hawaiian diets. Although diet richness was not signifi...
Novel methodologies now make it possible to track the complete geographical movements of seafood ... more Novel methodologies now make it possible to track the complete geographical movements of seafood species from reproduction to human consumption. Doing so will better inform consumers and assist resource managers in matching fisheries and conservation policies with natural borders and pathways, including stock boundaries, networks of marine protected areas, and fisheries management areas. Such mapping necessitates an unprecedented synthesis of natural and social sciences, including knowledge of adult fish population abundance and movements, egg output, larval dispersal, and recruitment to juvenile and adult habitats, as well as fisheries stock assessment, capture, and distribution through human social networks. The challenge is to fully integrate oceanography, population genetics, ecology, and social sciences with fisheries biology to reveal the patterns and mechanisms of “Fish Flow” from spawning to supper. As practitioners representing all five of these disciplines, we believe that...
Remotely sensed ocean color data are useful for monitoring water quality in coastal environments.... more Remotely sensed ocean color data are useful for monitoring water quality in coastal environments. However, moderate resolution (hundreds of meters to a few kilometers) satellite data are underutilized in these environments because of frequent data gaps from cloud cover and algorithm complexities in shallow waters. Aggregating satellite data over larger space and time scales is a common method to reduce data gaps and generate a more complete time series, but potentially smooths out the small-scale, episodic changes in water quality that can have ecological influences. By comparing aggregated satellite estimates of Kd(490) with related in-water measurements, we can understand the extent to which aggregation methods are viable for filling gaps while being able to characterize ecologically relevant water quality conditions. In this study, we tested a combination of six spatial and seven temporal scales for aggregating data from the VIIRS instrument at several coral reef locations in Mau...
Coral bleaching is the single largest global threat to coral reefs worldwide. Integrating the div... more Coral bleaching is the single largest global threat to coral reefs worldwide. Integrating the diverse body of work on coral bleaching is critical to understanding and combating this global problem. Yet investigating the drivers, patterns, and processes of coral bleaching poses a major challenge. A recent review of published experiments revealed a wide range of experimental variables used across studies. Such a wide range of approaches enhances discovery, but without full transparency in the experimental and analytical methods used, can also make comparisons among studies challenging. To increase comparability but not stifle innovation, we propose a common framework for coral bleaching experiments that includes consideration of coral provenance, experimental conditions, and husbandry. For example, reporting the number of genets used, collection site conditions, the experimental temperature offset(s) from the maximum monthly mean (MMM) of the collection site, experimental light condit...
Reef corals are mixotrophic organisms relying on symbiont-derived photoautotrophy and water colum... more Reef corals are mixotrophic organisms relying on symbiont-derived photoautotrophy and water column heterotrophy. Coral endosymbionts (Family: Symbiodiniaceae), while typically considered mutualists, display a range of species-specific and environmentally mediated opportunism in their interactions with coral hosts, potentially requiring corals to rely more on heterotrophy to avoid declines in performance. To test the influence of symbiont communities on coral physiology (tissue biomass, symbiont density, photopigmentation) and nutrition (δ13C, δ15N), we sampled Montipora capitata colonies dominated by a specialist symbiont Cladocopium spp. or a putative opportunist Durusdinium glynnii (hereafter, C- or D-colonies) from Kāne‘ohe Bay, Hawai‘i, across gradients in photosynthetically active radiation (PAR) during summer and winter. We report for the first time that isotope values of reef corals are influenced by Symbiodiniaceae communities, indicative of different autotrophic capacities ...
Dissolved organic matter (DOM) composition influences microbial community metabolism and benthic ... more Dissolved organic matter (DOM) composition influences microbial community metabolism and benthic primary producers are a source of DOM in coral reefs. As reef benthic communities change, in part due to nutrient pollution, understanding impacts on reef microbial processes requires knowledge of DOM sources and composition. We conducted a multi‐week mesocosm experiment dosing four coral reef benthic constituents with three levels of nitrate and phosphate to contrast exudate composition and quantify the effects of nutrient enrichment on exudate release. Moderate nutrient enrichment enhanced bulk dissolved organic carbon exudation by all producers. Corals exuded rapidly accumulating DOM with a markedly high concentration of aromatic amino acid‐like fluorescent DOM components that clearly distinguishes them from algal exudates, which were dominated by humic‐like fluorescent components and did not accumulate significantly. Our results indicate that corals and algae release DOM of different...
Endemic disease transmission is an important ecological process that is challenging to study beca... more Endemic disease transmission is an important ecological process that is challenging to study because of low occurrence rates. Here, we investigate the ecological drivers of two coral diseases -- growth anomalies and tissue loss -- affecting five coral species in Hawaii. We first show that a statistical framework called the case-control study design, commonly used in epidemiology but rarely applied to ecology, provided high predictive accuracy (68-84%) and disease detection rates (62-86%) compared with a traditional statistical approach that yielded high accuracy (98-100%) but low disease detection rates (0-13%). Using this framework, we found that larger corals were associated with higher disease risk across all host-disease pairs. We found that human activities in watersheds adjacent to shallow, semi-protected coral reefs were associated with growth anomalies whereas reef structure, water movement, and temperature exposure were associated with tissue loss. Variation in risk factors...
The deep reef refuge hypothesis (DRRH) postulates that mesophotic coral ecosystems (MCEs) may pro... more The deep reef refuge hypothesis (DRRH) postulates that mesophotic coral ecosystems (MCEs) may provide a refuge for shallow coral reefs (SCRs). Understanding this process is an important conservation tool given increasing threats to coral reefs. To establish a better framework to analyze the DRRH, we analyzed stony coral communities in American Sāmoa across MCEs and SCRs to describe the community similarity and species overlap to test the foundational assumption of the DRRH. We suggest a different approach to determine species as depth specialists or generalists that changes the conceptual role of MCEs and emphasizes their importance in conservation planning regardless of their role as a refuge or not. This further encourages a reconsideration of a broader framework for the DRRH. We found 12 species of corals exclusively on MCEs and 183 exclusively on SCRs with another 63 species overlapping between depth zones. Of these, 19 appear to have the greatest potential to serve as reseeding...
Corals build reefs through accretion of calcium carbonate (CaCO3) skeletons, but net reef growth ... more Corals build reefs through accretion of calcium carbonate (CaCO3) skeletons, but net reef growth also depends on bioerosion by grazers and borers and on secondary calcification by crustose coralline algae and other calcifying invertebrates. However, traditional field methods for quantifying secondary accretion and bioerosion confound both processes, do not measure them on the same time-scale, or are restricted to 2D methods. In a prior study, we compared multiple environmental drivers of net erosion using pre- and post-deployment micro-computed tomography scans (μCT; calculated as the % change in volume of experimental CaCO3 blocks) and found a shift from net accretion to net erosion with increasing ocean acidity. Here, we present a novel μCT method and detail a procedure that aligns and digitally subtracts pre- and post-deployment μCT scans and measures the simultaneous response of secondary accretion and bioerosion on blocks exposed to the same environmental variation over the sam...
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Papers by Megan Donahue